President Barack Obama said the strikes were needed to “disrupt plotting against the United States.” The Pentagon said Khorasan “was nearing the execution phase in an attack either in northern Europe, or the homeland.”

World leaders were meeting at a United Nations summit in New York. Support for the attacks was audible except from Russia, which condemned them as a violation of Syrian sovereignty.

An anonymous official on the Iranian side quoted by Reuters agrees with the earlier AP report quoting a US official as saying that the United States told Iran beforehand about its plan to strike in Syria. Reuters:

The United States informed Iran in advance of its intention to strike Islamic State militants in Syria and told Tehran that it would not target the forces of Syrian President Bashar al-Assad, a senior Iranian official told Reuters.

“Iran was concerned about Assad’s position and his government being weakened in case of any action against IS (Islamic State) inSyria and brought this issue up in meetings with Americans,” a senior Iranian official said on condition of anonymity.

“This issue was first discussed in Geneva and then was discussed thoroughly in New York where Iran was assured that Assad and his government will not be targeted in case of any military action against Daesh (Islamic State) in Syria.”

He added that Iran was informed separately in advance of the airstrike.

The official said funding for the strikes was provided jointly by the UAE, Kuwait, Saudi Arabia and Qatar. “The strikes have targeted mainly Islamist extremist groups in Syria as well as the Islamic State,” he said.

NATO ally Turkey, which is alarmed by Islamic State but also worried about Kurdish fighters and opposed to any action that might help Syrian President Bashar al Assad, had so far refused a military role in the coalition.

Turkey is home to a major U.S. base in the southern town of Incirlik, which officials have said has not been used so far in any lethal strikes in Iraq or Syria.

Erdogan said Turkey viewed the U.S.-led action positively and said it should continue.

Turkish officials has said its hands were tied while 46 of its citizens were held hostage by Islamic State militants in northern Iraq, including its consul general in Mosul, soldiers and diplomats’ children.

Alan Henning family issues message

The family of Alan Henning, the British aid volunteer kidnapped in 2012 and believed now to be held by Isis, have issued the following message to his captors:

I am Barbara Henning the wife of Alan Henning. I have a further message for Islamic State.

An audio file of Alan pleading for his life has just been received by me. I and people representing me continue to reach out to those holding Alan. Islamic State continue to ignore our pleas to open dialogue.

I have seen Muslims across the globe question Islamic State over Alan’s fate. The voices of the people have spoken out loud and clear. He was working with Muslims to help the most vulnerable within Syria. Nothing has changed. He went to Syria to help his Muslim friends deliver much needed aid.

We are at a loss why those leading Islamic State cannot open their hearts and minds to the facts surrounding Alan’s imprisonment and why they continue to threaten his life.

I have been told that he has been to a Sharia Court and found innocent of being a spy and declared to be no threat. I implore Islamic State to abide by the decisions of their own justice system.

Please release Alan.

Earlier Tuesday, the brother-in-law of Alan Henning spoke of his fears over US air strikes in Syria aimed at the militants’ strongholds, the Guardian’s Chris Johnston reported:

Colin Livesey said on Tuesday he was concerned that the action could prompt Isis to move Henning and make his whereabouts unknown once more. “I don’t want to lose the faith in knowing he’s coming home,” he told ITV News.

The Pentagon insists that its military focus remains on Iraq even as it expands operations to Syria, Guardian US national security editor Spencer Ackerman (@attackerman) reports:

“What you saw today and what you saw last night were a disruption to Isil forces that were enabling their strikes into Iraq,” Mayville said, using another name for Isis.

“We are focused first in Iraq because we have a partner in Iraq to work with, the Iraqi security forces, the Iraqi government, but we are striking through the depths of Isil’s formations, because we are trying to disrupt their support bases.”

Echoing comments from his boss, Gen Martin Dempsey, the chairman of the joint chiefs of staff, Mayville said he would think of the “credible and sustainable persistent campaign” against Isis “in terms of years”. [...]

US officials were cautious that Isis was a resilient enemy that is likely to adapt to US air attacks, something Mayville said was already on display in Iraq, the site of nearly 200 air strikes since 7 August. Yet despite forecasting a military campaign lasting years, there is no official designation for it, leaving confusion as to what to call the third major US war in Iraq in 23 years – a conflict that has emerged in defiance of Obama’s central 2008 vow to end the last one.

As our live blog coverage continues, here’s a summary of where things stand:

President Barack Obama officially notified Congress of a “systematic campaign of airstrikes” the administration plans to carry out in Syria and Iraq. “It is not possible to know the duration of these deployments and operations,” the president’s letter said.

President Barack Obama said the strikes were needed to “disrupt plotting against the United States.” The Pentagon said Khorasan “was nearing the execution phase in an attack either in northern Europe, or the homeland.”

Of the five coalition partners the United States has named, three – Bahrain, Jordan and Saudi Arabia – have acknowledged a role. Qatar and the UAE have not sought attention for their reported role.

The administration argues the strikes are justified under Article 51 of the U.N. Charter, which covers the individual or collective right of states to self-defense against armed attack.

World leaders are meeting at United Nations headquarters in New York, where attendees include the Iranian president, who was photographed meeting with his French counterpart.